1. Field of the Invention
The present invention relates to an apparatus for solidifying a casting to create a directionally solidified or single crystal casting and, more particularly, to an apparatus which is capable of introducing a cooling spool into a casting mold and withdrawing the casting mold from a stationary heating chamber.
2. Related Art
Solidifying molten materials, such as molten metal, in a mold cavity to create a directionally solidified or single crystal casting is known. FIGS. 1a and 1b illustrate a conventional apparatus 10 for producing a casting. An example of this is disclosed in U.S. Pat. No. 4,969,501. The apparatus 10 includes a heating chamber 12 defining an interior volume 16 which is heated via heating elements 14. A plurality of casting molds 20 are disposed in an annular array on a vertically movable chill plate 22. The molds are supported in and removable from the interior volume 16 by the movable plate 22. The movable plate 22 is vertically displaced by column 24. More particularly, the casting molds 20 may be removed from the interior volume 16 by displacing the plate 22 in the direction of arrow A (FIG. 1b) while the heating chamber 12 remains stationary.
Unfortunately, apparatus 10 produces directionally solidified or single crystal castings having less desirable material properties due to a lower thermal gradient during casting. A thermal baffle or heat sink is not introduced into an interior region of the casting mold apparatus during the withdrawal from the heating chamber 12 to selectively absorb radiant heat being supplied from the molds 20. Indeed, order to obtain a directionally solidified or single crystal casting, a casting mold must be removed from a heating chamber using special procedures.
FIGS. 2a and 2b show another conventional apparatus 50 to produce a directionally solidified or single crystal casting. An example of this is disclosed in U.S. Pat. No. 5,778,961. The apparatus 50 includes a heating chamber 12 defining an interior volume 16 for receiving an annular array of casting molds 20. The casting molds 20 surround and define an interior space 21. The molds are disposed on a chill plate or disk 30 which includes a central aperture 31. A thermal baffle or heat sink 34 is shaped and sized to pass through the aperture 31 in the plate 30, and the baffle is movable vertically upward in the direction of arrow C (FIG. 2b) with respect to the plate 30 by its supporting column 36. In particular, the thermal baffle 34 may be moved into the interior space 21 by moving the column 36 upward, and vice versa. The radiation baffle 19 is disposed below the open end of the heating chamber 12.
The casting molds 20 are maintained in a substantially fixed position and height with respect to a floor 32. The casting molds 20 are removed from the interior volume 16 of the heating chamber 12 by raising the heating chamber 12 in the direction of arrow B (FIG. 2b). Thermal baffle 34 may be moved into interior space 21 while the heating chamber 12 is moved.
Apparatus 50 is also less desirable for preparing directionally solidified or single crystal castings because the heating chamber 12 must be lifted away from the casting molds 20 while the molds 20 are fixed in height and position with respect to floor 32 which is contrary to industry practice. The investment casting industry more widely accepts withdrawal processes in which the casting molds 20 are moved downward out of the heating chamber 12, and would be unable to retrofit existing furnaces to provide a heating chamber 12 which must be lifted.
Accordingly, there is a need in the art for a directionally solidified or single crystal casting apparatus which allows for withdrawing casting molds from a substantially fixed heating chamber.